Improvement in restoring spent alkalies



. A. s. LYMAN. y A Restoring Spent Alkalies- Pa'tented Dec. 22, 1874.

l l l L l l l l I1 UNITED STATES PATENT OEEio AZEL STORRS LYMAN, OF NEW YORK, ASSIGNOR TO ADDISON H. LAFLIN, OF HERKIMER, NEW YORK.

IMPROVEMENT IN RESTORING SPENT ALKALIES.

Specification forming part of Letters Patent No. 157,919, dated December 22, 1874; application led May 4, 1874.

To all whom it may concern:

Beit known that I, AZEL STORES LYMAN, of the city, county, and State of New York, have invented certain new and useful Improvements in the Art of Restoring Spent Alkali, of which the following is a specification:

This invention consists in a process by means of which the alkalies so extensively used in the arts for bleaching and other purposes, and which in such use become dilute with water and mingled with various foreign organic matters, may be restored or recovered cheaply and expeditiously, and in condition for reuse.

The expense attending the previously-kn0wn modes of reclaiming spent alkali has been so great as nearly, or quite, to equal the value of fresh alkali, and, as a consequence, large quantities of spent alkali have been thrown away, as not warranting the application of those processes of recovering the original salt.

By the improvements hereinafter described, a large saving can be effected both for the manufacturer and the consumer.

The irst part of the improved process consists in the mode by which the preliminary concentration of the liquor is effected. ln order to restore dilute alkali containing foreign matters, the usual process is to evaporate the larger portion of the water, thereby reducing the solution to a viscous or pasty condition, and then subject the residuum to the direct action of lire upon the calcining-hearth, and thus burn out the organic substances, at the same time completing the evaporation. This partial preliminary concentration has usually been performed in one of two ways: Either by distributing the liquor in large shallow evapora-ting-pans, the bottoms of which are exposed to the direct impact of the iiame or of the ascending products of combustion, or by causing it to flow down through a tower or stack, the interior construction of which is such that the descending liquor will follow a zigzag or an irregular and tortuous course, (as by the use of shelves extending alternately from two opposite sides of the inclosed space of the tower,) while a draft of air, passing up-` ward through the tower, meets the descending liquor, and thus carries off much of the water. This exposure of the dilute alkali to currents of air, by means of shallow pans, or of shelves on which it descends by the force of gravity from one to another, does not afford the requisite facility for regulating the degree of concentration, and otherwise is found to be an exceedingly expensive process. As opposed to both of these modes, the improved process consists, in its first branch, in lifting or throwing the liquor up from the receivingvat, in a iinely-subdivided condition, by the use of Vrevolving disks, or other equivalent devices, located within or over the vat, and causing currents of air to sweep in among the spray thus produced, or among the thin films or sheets of the liquor. As these disks or other agitators are to be arranged above -or within the receiving vat, the liquor when thrown or carried up will return to the same vat by its own weight, and thus the process can be carried on until the liquor is brought down to any desired degree of concentration. When reduced to a pasty or viscous condition, it is to be thrown down, discharged or dumped upon the calcining hearth, and there exposed in the well-known mode to the direct action of the lire, by which the evaporation is completed, and the foreign matters burned out.

The second branch of the improved process consists in the mode adopted for preventing the escape of alkali from the calcining-hearth. It has been discovered that while the process of incineration is going on, a large portion of the alkali (estimated to exceed twenty-live per cent.) is caught up by the escaping products of combustion, being mechanically mixed therewith, and carried by them into the uptake.

In order to prevent this enormous loss, the present invention proposes to send the products of combustion through a filter or straining-stack, composed of coke, broken stone, wire-gauze, or any suitable material that will cause them to travel for some considerable distance iu'a fmely'subdivided state. This filter or stack is to be kept moistened by the downward flow of water, or of the alkali either in its dilute or its partially concentrated state, and as the descending liquid is thus brought into intimate contact with the ascending and finely-subdivided products of combustion, it will wash out the particles of alkali, which are merely held in suspension, and carry them back again to the calcining-hearth.,

lf desired, iu order to prevent the liquor thusemployed in arresting the escape of the alkali from reaching. the calcining-hearthv in too dilute a condition, a concentrating apparatus may be placed at the base of the straining-stack, in which the wash of the stack may be caught, and', by means of revolving disks or otherwise, subjected to the action of the heated currents of air until sufficiently concentrated.

It may be found the most economical in practice to arrange this filter or strainingsta'ck between the receiving-vat, in which the preliminary concentration of the dilute alkali takes place, and the calcining-hearth, in order that the partially concentrated liquor from the receiving-vat may be discharged upon the top of the filter, and thus be made to serve as the medium for washing out the alkali from the escaping products of combustion. This arrangement would be specially economical, since the exposure of the partially-concentrated liquor to direct contact with the highly-heated products of combustion would greatly facilitate the evaporation of the water, and would entirely obviate the necessity of using pure water as a wash, which, if used, would require a large amount of heat for its subsequent evaporation.

In the accompanying drawing, Figure l is a longitudinal vertical section of an apparatus for restoring spent alkali bythe improved process above described; Fig. 2 being a vertical transverse section of the same.

Referring to the several particular parts, that portion of the apparatus by which the preliminary partial concentration of the dilute alkali is effected is made up as follows: B is the vat or pan in which the dilute alkali is irst received, and from which, when partially concentrated, it can be drawn off through the pipes a a. A is one of a series of revolving disks, the lower segments of which dip in the solution in the vat. These disks may be made of wood or of metal, or any suitable material, and their surfaces may, if desired, be corrugated, in order the better to take up the'liquor, and to expose a greater surface to the action of the air. C G are a series of horizontally-revolvin g fans, mounted in a frame above the disks, their ofice being to draw currents of air in, among, and through the liquor, when lifted up in thin films upon the disks, or otherwise presented in a finely-subdivided condition to the action of the air-currents. The efficiency of the fans in this particular is largely increased by the use of a hood, as shown inthe drawing, which covers the disks, and serves to cause the whole body of the moving air to enter the agitated liquor. For the purpose of facilitating the evaporation,the liquor in the receiving tank or vat may be heated. This may be done either by passing the products of combustion under the vat or by a coil of pipe, b b, placed withinthe vat, and supplied with either exhaust or live steam, or, as shown in the drawing, by a combination of both of these means.

The degree to which the concentration of the liquor is to be carried in the receiving-vat Will depend upon circumstances. If, on the one hand, the contents of the vat are to be passed directly to the calcining-hearth, they must be brought into a viscous or pasty condition; if, on the other hand, they are to be Y used in the filter or straining stack for washing the alkali out of the escaping products of combustion, they should be taken from the vat while yet in a more fluid condition. Instead of revolving disks and fans, as shown in the drawing, any other suitable apparatus may be employed that will agitate the liquor contained in the Vat, and by this means present it in a finely-subdivided condition to the action of currents of air passing into and through it.

Referring again to the drawing, the parts constituting and connected with the strainingstack are as follows: F is the filter or stack itself, which may be composed of puinicestone, coke, fine gravel, sieves of wire-gauze of fine mesh, or of any suitable material and structure, adapted to cause a descending current of liquid to pass down slowly, and to become in its descent very finely subdivided. This filter rests upon a perforated metal foundation, or upon iron bars, after the seinblance of lire-grate bars. E is a sprinkler, consisting substantially of a box having a finely-perforated bottom, being designed for securing the even distribution of the liquOl over the upper surface of the stack. D is an oscillating trough for aiding the action of the sprinkler E. This trough is divided into two longitudinal compartments, and has an oscillation upon its axle, through something less than one-fourth of a circle, but sufficient to throw out the contents of the filled compartment at each oscillation. Beneath the stack is placed a concave receiver, H, in which the liquor is caughtY after percolating through the stack. This concave is loosely hung to the shaft c, and revolving with it are a series of small disks, one of which is represented by G, that dip into the contents of the receiver H, and operate upon them in substantially the same way as the larger disks A do upon the contents of the vat B.

By means of these small disks G, which may be continuously operated or allowed to stand at rest at pleasure, the concentration of the liquor that has passed down through the stack may be carried to any desired extent prior to discharging the same upon the calcining-hearth. The condition of the alkali when upon the disks G can be ascertained by opening the doors O in the wall behind the disks 5 and the contents of the receiver H can be dropped upon the hearth below, Whenever desired, by pushing the receiver forward, and causing, it to make a partial revolution on the shaft c. As shown in the drawing, the strainin g-stack is arranged in immediate connection with the receiving-vat, in which the partial concentration first takes place. This is the preferred arrangement, since by means thereof the partially-concentrated liquor may be used for washing the products of combustion, and thus arresting the escape of alkali from the calcining-hearth. If, however, under any other arrangement of parts a more dilute liquor should be employedfor this purpose, it might be used over and over again, being repeatedly returned from the receiver H to the top of the stack until brought at last to such consistency as to be fitted for the tinal process of incineration. The incineration of the alkali when it has reached the calcining-hearth is performed in the usual manner. In the drawing, L and R represent the hearth or sole of a reverberatory furnace adapted to this purpose, the re-box and grate being shown at K. The partially-concentrated alkali is dropped in a viscous or semi-fluid condition upon the rear part of the hearth. The fire, passing over it, quickly dries out the remaining moisture, entirely destroying all the fluidit f of the mass. It is then pushed forward over the rise It by means of convenient tools inserted through the doors N, and spread upon the portion of the hearth next the fire-box. Here itis exposed to the intense heat of the re, and whatever combustible and organic matters it contains, by reason of its previous use, are burned out, leavinga residuum of carbonate of soda, which may be removed by Scrapers inserted through the doors n n in the side of the furnace.

What is claimed as new is l. The hereinbefore-described process of reclaiming spent alkali, the same consisting in exposing the solution in the receiving-vat, in a finely-subdivided state, by means of revolving disks or equivalent devices, to currents of air until it is partially concentrated, and then completing the restoring process by incineratlon.

2. The hereinbeforedescribed mode of preparing spent alkali for incineration in the process of reclaiming it, the same consisting in exposing the solution in a nely-subdivided state to currents of atmospheric air, and subsequently passing it through a stack of coke, broken stone, wire-gauze, or other similar material, in contact with the escaping products of combustion, substantially as and for the purpose set forth.

3. The hereinbeforefdescribed mode of arresting the escape of alkali from the incinerating-i'urnace by causing the products of combustion to pass through a lter or strainingstack of coke, broken stone, wire-gauze, or othersimilar material, which is kept moistened by the downward flow of water or of dilute alkali, by means of which the products of combustion are washed, and the escaping alkali caught and saved.

4. Ina furnace for restoring spent alkali, the combination and arrangement, substantially as shown and described, of the receivingvat for holding the dilute liquor, the revolving disks or equivalent devices for raising the solution and exposing it to currents of air, and the incinerating-hearth, for burning out the organic matters from the partiallyconcentrated mass and completing the evaporation.

5. In combination with the incineratinghearth of a furnace for recovering spent alkali, a filter or straining-stack of coke, broken stone, wire-gauze, or other material of similar character, through which the products of combustion are made to pass, for the purpose of arresting the escape of the alkali, substantially as hereinbefore set forth.

6. In combination with the filter or straining-stack, through which the products of combustion pass on their escape from the calcining-hearth, the oscillating distributing-trough, for effecting the even distribution of the liquor over the surface of the filter.

7. In combination with the iilter or straining-stack, through which the products of combustion pass on their escape from the calcining-hearth, the receiving-trough and revolving disks, arranged below the filter, for receiving and further concentrating the liquor which has 4descended through the filter.

8. In combination with the revolving disks arranged below the filter or straining-stack, a receiving-trough, constructed and arranged to tilt, substantially as shown and described, for the discharge of the partially-concentrated mass upon the calcining-hearth.

AZEL STORES LYMAN.

Witnesses SAML. A. DUNCAN, B. G. NOBLE. 

